He eventually rose to the admiralty, and by the 2330s, was in command of Starbase 53. At that time, Admiral Harriman was still heavily involved in Starfleet Intelligence, and recruited numerous operatives, including Mark Coleman, who became his protégé.

In 2341, Harriman had Coleman reassigned from the investigation of Enclave J-12 and the death of Jacob Sinclair. Harriman later recommended Coleman for the admiralty in 2356.